Mint plant named &#34;metolius&#34;

ABSTRACT

A new and distinct variety of  Mentha canadensis  (‘Metolius’) is characterized by its unique oil chemistry and flavor profile resembling that of peppermint oil, and by its tolerance to Verticillium wilt ( Verticillium dahliae ) and mint rust ( Puccinia menthae ). DNA microsatellite marker analysis has shown that ‘Metolius’ is a distinct variety of  M. canadensis.

LATIN NAME OF THE GENUS AND SPECIES OF THE PLANT CLAIMED

Mentha canadensis

VARIETY DETERMINATION

‘Metolius’

FIELD OF THE INVENTION

The present invention relates to a new and distinct mint botanically known as Mentha canadensis. The new variety has been named ‘Metolius’ and will be referred as such hereafter.

BACKGROUND OF THE INVENTION

The present invention is a new variety of the mint species Mentha canadensis (common name American cornmint/Japanese peppermint). The essential oil industry refers to some members of the Mentha canadensis species as “Mentha arvensis.” This includes such popular varieties as ‘Shivalik,’ ‘Kosi,’ and ‘Kalka.’ Botanically, however, these plants are M. canadensis species, with Mentha arvensis being a different and significantly less commercial mint species commonly referred to as a cornmint. The botanical differences allow one to differentiate between the two species through the use of current botanical keys for the genus Mentha. The use of “Mentha arvensis” by the industry should be interpreted as a colloquial industry usage for an “oil type” and not one of botanical specificity as these plants are correctly botanically identified as M. canadensis. For further information on mint species, see Lawrence, B. ed., 2007. Mint: The Genus Mentha. CRC Press, Boca Raton, Fla; see also Tucker, A. O. and T. Debaggio, 2000. The Big Book of Herbs. Interweave Press, Inc., Loveland, Colo.

The new mint plant of the present invention was developed in an effort to cultivate a mint variety having a peppermint type oil and flavor profile, and greater tolerance to Verticillium wilt (Verticillium dahliae) and mint rust (Puccinia menthae) compared to that of commercial peppermint (Mentha piperita). Furthermore, ‘Metolius’ produces a peppermint-type oil that varies minimally in oil profile based on plant maturity.

The inventors explored ways of creating genetically distinct mint plants through somatic hybridization of unpatented varieties of Mentha canadensis and Mentha piperita. In 2002 ‘Metolius’ was created using this method. Specifically, the parental stock that was used to create ‘Metolius’ consisted of unpatented germplasms of Mentha×piperita and Mentha canadensis species. The features of ‘Metolius’ are compared to the parentMentha canadensis.

Since 2002, the plant has been under continuous evaluation at the Applicants' facilities in Eugene, Oreg. and Sunnyside, Wash., as well as under small-scale commercial programs located in Idaho, Washington, and Eastern Oregon. Asexual propagation through stem and rhizome cuttings have been successfully carried out many times in Eugene, Oreg. and Sunnyside, Wash. The resulting propagules have remained stable in appearance, oil quality, and other characteristics to the original plant.

SUMMARY OF THE INVENTION

The present invention relates to a new and distinct mint plant named ‘Metolius’ characterized by a unique oil chemistry and flavor profile resembling that of peppermint oil, and by its tolerance to Verticillium wilt (Verticillium dahliae) and mint rust (Puccinia menthae). Compared to ‘Shivalik’ and ‘Kosi,’ two commonly grown commercial varieties of M. canadensis, the plant is slightly shorter with darker green leaves when grown under similar growing conditions. The leaves are also slightly longer and narrower compared to ‘Shivalik.’ It matures about the same time as ‘Shivalik’ and ‘Kosi.’ The oil chemistry and flavor profile of ‘Metolius’ is also similar throughout its maturity when grown in Oregon, Washington, and Idaho.

BRIEF DESCRIPTION OF THE PHOTOGRAPHS

The accompanying color photographs of ‘Metolius’ show the new variety:

FIG. 1: shows the flower spike of ‘Metolius’.

FIG. 2: shows the mature leaves of ‘Metolius’.

DETAILED DESCRIPTION OF THE INVENTION

The present invention ‘Metolius’ is a new and distinct variety of a Mentha canadensis plant having the following characteristics that, in combination, are not exhibited in other M. canadensis plants.

l-Menthone to d-Isomenthone ratio of around 4.5%, typical of that found in commercial peppermint (Mentha piperita) oil. In other commercial Mentha canadensis, this ratio is around 2.0% or less.

l-Menthone of about 18% to 20%, compared to about 8% to 10% for other commercial M. canadensis.

l-Menthol of about 62%, this compared to 42% and 72% for commercial peppermint and other commercial M. canadensis respectively.

l-Limonene of about 2.5% compared to 1.5% and under 2.0% for peppermint and other commercial M. canadensis respectively.

Oil having a clean peppermint-like flavor and odor profile.

When grown side by side with other commercial M. canadensis, ‘Metolius’ is a slightly shorter plant with leaves slightly darker, shorter, and narrower.

-   Botanical description: M. canadensis ‘Metolius’ is an herbaceous     perennial with an upright shrubby growth habit. The plant physically     spreads by stolons and it is reasonable for a single rooted cutting     to spread and cover 3-4 square feet after one growing season.     Numerous branching stems are produced each year with an eventual     height of 70-80cm. Compared to ‘Shivalik’ (not patented) and ‘Kosi’     (U.S. Plant Pat. No. 12,426), two commonly grown commercial     cornmints, the plant is slightly shorter with darker green leaves     when grown under similar growing conditions. The leaves are also     slightly longer and narrower compared to ‘Shivalik.’ It matures     about the same time as ‘Shivalik’ and ‘Kosi.’ ‘Metolius’ has been     grown in different field locations. It has also been grown under     greenhouse conditions. Asexual propagation through stem and rhizome     cuttings have been successfully carried out many times since 2002 at     the Applicants' facilities in Eugene, Oreg. and Sunnyside, Wash. The     resulting propagules have remained stable in appearance, oil     quality, and other characteristics to the original plant. The basic     morphological characteristics have remained consistent, with any     minor differences easily attributed to differences such as climate,     soils, fertilizer, or water regime. The distinguishing traits     present in ‘Metolius’ remain constant in the asexually reproduced     plants. -   Oil composition and flavor: Although ‘Metolius’ has the same     chemical components as other M. canadensis varieties, the relative     amount of several components resembles the distribution typically     found with peppermint oil. The l-Menthone/d-Isomenthone ratio of     about 4.5 for ‘Metolius’ is typical of a standard Mentha piperita     which contributes to the clean peppermint-like flavor     characteristics noted with this oil. The level of l-Menthone is     about 18.0% for both ‘Metolius’ and commercial peppermint compared     to 10% for other commercial M. canadensis varieties. The level of     l-Menthol is about 62%, for ‘Metolius’ compared with 42% and 72% for     peppermint and other commercial M. canadensis, respectively. The     l/limonene level for ‘Metolius’ is about 2.5% compared to 1.5% and     less than 2.0% for peppermint and other commercial M. canadensis     respectively. -   Stem and leaves: ‘Metolius’ has a square stem and therefore does not     have a stem diameter. The stem dimensions measure 8-9 mm long per     side of the square for a total dimension of 8-9 mm by 8-9 mm when     mature. Measurements were taken near the base of the stem, since     this measurement will decrease towards the tip of the plant. The     plant matures to approximately 70-80 cm in length. Internode length     varies considerably along the stem from less than 20 mm near the     base and at the apex, increasing to an average of 50 mm along the     midstem. Under crowded conditions, internode length can even be     higher, up to 80 mm. As a mint plant, ‘Metolius’ spreads by     underground stolons and the number of stems is highly variable.     Stems and ovate leaves are pubescent, oppositely arranged on the     stem with an equilateral base, an acute apex, serrate margin and     decreasing in size towards the apex of a blooming stem. The average     mature leaf length is 60 mm. Average leaf width is 30 mm. Venation     pattern is pinnate. Dorsal leaf surface color is medium yellow green     (147A — Yellow-Green Group), with a lighter ventral color (147B —     Yellow-Green Group). Vein color is light yellow green (147C — Yellow     Green Group). The mature petiole length is 6-8 mm. Petiole width is     3-4 mm. Petiole thickness is 1-2 mm. Petiole color is light yellow     green (147C — Yellow-Green Group). Stem color is also light yellow     green (1460 — Yellow-Green Group). Color numbers are from the R.H.S.     Colour Chart (Royal Horticultural Society (Great Britain), London     1966). The base of the stem has a more “woody” appearance and     quality with more brownish coloring and fissures. The fragrance is a     clean peppermint-like aroma. -   Flower: Like other Mentha canadensis species, ‘Metolius’ possesses a     flower spike with a pair of bract-like leaves subtending each     verticillaster. The individual flowers contain a 4-lobed, nearly     regular, mostly white, tubular corolla with a slight light purple     coloration near the base (85C — Violet Group). The flower is 8 mm     long from the base of the calyx to the tip of the forked white     stigma. The calyx generally has five teeth fused at the base forming     a short tube and is 3 mm long. The calyx, peduncle and pedicel     colors are light yellow green (147C — Yellow-Green Group). Each     flower has one pistil with an 8 mm long white style and four     epipetalous stamens that are exerted with 4 mm long white filaments.     The white anthers are less than 1 mm. Pollen is not produced in     abundance. That which is produced has a pale yellow color. The     formation of seed is a rare event. There is no obvious flower     fragrance. The above description is based on observations of a field     plot made during the middle of the second growing season of the     field plot outdoors in western Oregon. -   Genetic analysis: In order to determine the precise genetic identity     of ‘Metolius’, DNA (SSR) microsatellite marker analysis was     conducted using known methods as described by T. A. Holton, Plant     genotypizng by analysis of microsatellites 15-28, in Plant     Genotyping: The DNA fingerprinting of plants (R. H. Henry ed.,     2001). Comparing microsatellite DNA (SSR) methodologies with other     DNA genotyping techniques such as RFLPs, AFLPs, and RAPDs, has     established that microsatellite DNA (SSR) offers a more reliable,     repeatable method for characterization with an increased ability to     differentiate among plant varieties. The technique has been widely     used in animal, plant, and human identification and population     studies. The drawback of the technique is the initial high cost of     developing the markers. However, once these markers have been     developed, they can be simply used by combining PCR with GenScan     technologies. During 2003-2005 period, a project was conducted using     34 microsatellite markers to genetically identify ‘Metolius.’ A     total of 4 different populations of M. canadensis were collected.     Their microsatellite DNA profiles were then compared against a total     of 8 recognized peppermint varieties along with other closely     related Mentha species including spearmint (M. spicata). A total of     179 microsatellite characters/profiles were found from the 34     markers. Genetic distances as measured by total character     differences among different populations of the same variety ranged     from 0-14. The values among recognized peppermint varieties ranged     from 16-42. The values between ‘Metolius’ populations and other M.     canadensis populations ranged from 0-4. A phylogenetic analysis was     conducted as well as a principal component analysis. Both revealed     that ‘Metolius’ and M. canadensis populations clustered together and     formed a strongly supported M. canadensis species group. Based on     these genetic analyses, ‘Metolius’ was classified as a variety of M.     canadensis. The differences observed among the M. canadensis samples     are typical of the differences noted among different varieties of     the same species, and allow the identification of ‘Metolius’ from     other varieties of M. canadensis. -   Plant disease resistance/susceptibility: Observations of ‘Metolius’     since 2002 indicate that rust does not infect ‘Metolius’ under any     observed circumstances. Furthermore, ‘Metolius’ has exhibited high     tolerance to Verticillum wilt through the same observation period. -   Winter hardiness and drought/heat tolerance: ‘Metolius’ is winter     hardy and heat tolerant in the common mint growing regions of the     world. No specific claims are made to exceptional cold hardiness or     heat tolerance. 

1. A new and distinct Mentha canadensis plant named ‘Metolius’ substantially as herein and described and illustrated. 